Solar parabolic cooker with the mechanical mathematician!

Step 5 Making the mechanical mathematician!

The mathematician can be made in many ways. Mine includes a piece of waste trim that is the slide bar at the top, a T-joiner for plastic pipes and a curtan rail that fit snugly into the T-Joiner. The string is strung from a hook on the central post at your favoured focal point, through a hole in the curtain rod and is tied on to the top of the T-Joiner. Some rules! The T-Joiner has to be at right angles to the slide bar which in turn must be at right angles to the central post.
Directly under the hooks on the central post, there is a screw which goes down about a half inch through the bottom of the wood piece at the bottom of the post.
And right under that screw, there is a hole in the dark piece of wood (just a little bigger than the screw). The dark piece of wood sits on the aluminium foil, screw goes in the hole and the top gaget can swivel around while the bottom piece stays in one spot. (This means less scuffing of the foil when the mathematician takes measurements!)